fix: run Github workflow for docs inside alpine (LCG podio too old)

This runs the doxygen workflow inside an alpine container based on the build products from eic-shell.

.github/workflows/linux-eic-shell.yml

 name: linux-eic-shell
 
-on: [push, pull_request]
+on:
+  push:
+  pull_request:
+  schedule:
+    - cron: '41 4 * * 0'
 
 jobs:
   build-test:
@@ -18,9 +22,56 @@ jobs:
     - uses: actions/upload-artifact@v3
       with:
         name: build-eic-shell
+        path: build/
+        if-no-files-found: error
+    - uses: actions/upload-artifact@v3
+      with:
+        name: install-eic-shell
         path: install/
         if-no-files-found: error
 
+  build-docs:
+    runs-on: ubuntu-latest
+    needs: build-test
+    container: alpine:latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/download-artifact@v3
+      with:
+        name: build-eic-shell
+        path: build/
+    - run: |
+        apk add doxygen graphviz
+        doxygen build/Doxyfile
+    - uses: actions/upload-artifact@v3
+      with:
+        name: docs-eic-shell
+        path: build/docs/html/
+        if-no-files-found: error
+    - run: |
+        apk add bash
+        # FIXME tracking https://github.com/actions/upload-pages-artifact/pull/14
+    - uses: actions/upload-pages-artifact@v1
+      if: github.ref == 'refs/heads/master'
+      with:
+        path: build/docs/html/
+        retention-days: 7
+
+  deploy-docs:
+    needs: build-docs
+    if: github.ref == 'refs/heads/master'
+    permissions:
+      pages: write
+      id-token: write
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    steps:
+    - name: Deploy to GitHub Pages
+      id: deployment
+      uses: actions/deploy-pages@v1
+
   trigger-juggler:
     runs-on: ubuntu-latest
     needs: build-test